Long‐term change in metabolism phenology in north temperate lakes

Abstract

The phenology of dissolved oxygen (DO) dynamics and metabolism in north temperate lakes offers a basis for comparing metabolic cycles over multi-year time scales. Although proximal control over lake DO can be attributed to metabolism and physical processes, how those processes evolve over decades largely remains unexplored. Metabolism phenology may reveal the importance of coherence among lakes and facilitate general conclusions about the controls on lake metabolism at regional scales. We developed a Bayesian modeling framework to estimate DO concentrations and metabolism in eight lakes in contrasting landscapes in Wisconsin, USA. We identify the DO and metabolism phenologies for each lake, and use those to compare how decadal patterns relate to trophic state and landscape setting. We show that lakes can be categorized by their hypolimnetic oxygen consumption dynamics, with oligotrophic lakes having a diverse set of patterns and eutrophic lakes having uniform trends of increased oxygen consumption over the last decade. Metabolism phenology is likewise diverse for oligotrophic lakes, whereas eutrophic lakes in southern Wisconsin share consistent long-term patterns of metabolic trends and seasonal DO consumption highlighting the importance of trophic state driving metabolism. Eutrophic lakes had higher magnitudes and more seasonal variation in net ecosystem production in contrast to oligotrophic lakes. Generally, long-term metabolic trends of north temperate lakes suggest a limited influence of climate on lake metabolism and that temporal coherence of long-term metabolism change is driven primarily by the landscape setting.

Comparing Drivers of Spatial Variability in U.S. Lake and Stream Phosphorus Concentrations

“…Outside of historic watershed loading, the fact that lacustrine systems internally recycle a large fraction of legacy P, likely only further obfuscates the relationship between contemporary inputs and current concentrations (Carleton & Lee, 2023). Similar processes have been forwarded in recent work comparing metabolism trends in pristine and highly impacted lakes in Wisconsin, where lakes biological processes seemingly are less responsive to shifts in nutrient inputs and climate (Ladwig et al, 2022). This internal recycling of legacy P may confound successful efforts to reduce agricultural inputs upstream in the watershed and delay expected improvements in lake total phosphorus concentrations.…”

The aftermath of a trophic cascade: Increased anoxia following species invasion of a eutrophic lake

“…Notable shifts in nutrient concentrations and oxygen dynamics in Lake Mendota have also been observed (Hanson et al, 2020; Ladwig et al, 2022). Ladwig et al (2021a) applied a mechanistic aquatic ecosystem model that was able to replicate hypolimnetic dissolved oxygen (DO) consumption and bottom-water anoxia from 1995 to 2015, but the model performance declined post-2009, with the model overestimating hypolimnetic oxygen concentrations.…”

Heat Waves Can Cause Hypoxia in Shallow Lakes

“…By integrating the results of high‐frequency monitoring of meteorological conditions, water temperatures, DO concentrations, and phytoplankton biomass into a simulation, we were able to analyze how heat waves could impact the thermal stability of the water column and the DO b concentration. We used a one–dimensional numerical simulation model to investigate how meteorological conditions affected the DO b concentrations (Antonopoulos & Gianniou, 2003; Dong et al., 2020; Fang & Stefan, 2009; Ladwig et al., 2022; Stefan & Fang, 1994). We also collected meteorological data from 1992 to 2022 and estimated how heat waves affected stratification and the supply/consumption of DO b .…”